Apparatus for heat treating



Nov. 7, 1939. A. c. DAMES APPARATUS FOR HEAT TREATING Original FiledJune 10, 1935 2 Sheets-Sheet 1 m m E %.0 W n e M Nov. 7, 1939. A. c.DAMES 2.179.073

APPARATUS FOR HEAT TREATING I Original Filed June 10, 1935 2Sheets-Sheet 2 IN VENTOR. A Mar! 6'. flamed IATTORNEYS Patented Nov. 7,1939 UNITED STATES PATENT OFFICE APPARATUS i on nan mama Albert 0.Detroit, 1mm, auignor to The Timon-Detroit Axle Company,

a corporation of Ohio Detroit, Mich Application June 10, 1935, SerialNo. 25,921 Renewed April 6, 1939 12 Claim.

' parts which are required to be extremely hard at tion to anintermediate value.

one portion and comparatively soft at others. Such parts are, forexample, gears wherein only the gear teeth need be hard, camshaftswherein only the cams need be hard, and steering balls wherein only theball portions need be hard.- The usual method of obtaining the requisitehardness is by carburization, or as it is sometimes calledcasehardening.

When a combination of hardnesses is sought in a single piece as in agear or a steering ball, either of two methods have heretofore beenused.

The first is to copper or tin plate the portions which are to remainsoft, place the entire article in a carburizing pot, and place the potin a heattreating furnace for a period of hours. Carburization will nottake place where the part has been copper-plated. This process requiresthat after carburization the copper-plating must be removed from thesoft portions, as by grinding, and then the soft portions annealed, orfurther heattreated in case a medium hardness is required at suchportions.

The second method is to carburize the entire piece and then, aftercarburization, draw, as by immersing only the portions to be softened ina pot of heated lead, and quench in air. This reduces the extremehardness gained by carburiza- It is necessary, after the lead pot drawto perform a wire-brushing operation in order to remove particles oflead which may adhere to the article.

Either of the above two methods is necessarily costly as they entail amaterial amount of direct labor which is an item to be avoided whereverpossible under present mass production policies. In removing thenecessity for such labor and in accordingly effecting economies, aprimary object of my invention is to provide novel apparatus forselectively carburizing articles of manufacture without plating wherebyonly such portions of said articles are carburized as requirecarburizing, and the remainder thereof are left comparatively soft.

A further object is to provide novel apparatus for selectivelycarburizing articles of manufacture wherein substantial variations ofhardness may be imparted to different portions of a single articlesimultaneously, thereby eliminating operations hitherto considerednecessary, such as copper or tin-plating, or lead pot drawing andwire-brushing, or in fact, all subsequent heat treatment.

A further object is to provide novel carburizing apparatus wherein onlythose portions of the article to be heat treated as by carburizing, areencased within carburizing compound and the remainder thereof is free ofcompound, but protected from an oxidizing atmosphere.

Still a further object is the provision of novel heat treating apparatuswherein only selected portions of an article to be heat treated areplaced in contact with carburizing compound and where-. in compound-freeportions are hardened to a degree different from that of the compoundencased portion.

A further object of my invention is to provide novel carburizingapparatus wherein means is provided for individual handling of thearticles to be carburized, the means conforming in contour substantiallyto the shape of the articles.

Due to the high temperatures required for carburizing, the life of thecontainers employed is relatively short in spite of the development ofspecial materials for this purpose. The old type of container, namely, alarge box in which a number of pieces are packed with carburizingcompound separating them, has perhaps as long a life as any containersince made. However, these containers are very inemcient, as there is alarge loss of compound per individual heat, due to the fact that the boxmust be dumpedat least in part-before the articles may be removed. Also,individual handling of the carburized articles is impossible with theresult that. such containers have a high percentage rejection, and agreat deal of straightening, grinding and other reconditioningoperations are necessary upon the carburized pieces.

An improvement on this form of apparatus is the invention disclosed inthe copending application of Harry W. McQuaid, Serial No. 692,329, filedOctober 5, 1933. In this type of apparatus individual handling of theparts is obtained and the loss of compound and the percentage rejectionis reduced. The results from the use of the present invention are evenbetter than those resulting. from a practice of the McQuaid invention inthat the containers employed have been found to be characterized by alonger life and a tendency not to warp or lose their alignment in spiteof the heat to which they are repeatedly subjected. It is therefore amajor object of my invention to provide novel carburizing apparatuswherein individual containers may be employed with a life far alignmentdue tothe repeated subjections to heat are eliminated.

A further object is to provide novel carburizing apparatus which reducesthe cost of actual carburizing operations and eliminates any necessityfor further heat treatment or reconditioning by way of machining.

Still a further object of my invention resides in the provision of anovel container for containing an article to be carburized, thecontainer being designed to cooperate with the article wherebycarburizing compound introduced into contact with a selected portion ofthe article is prevented from contacting other portions of the article.

A further object of my invention resides in the provision of a novelcarburizing container for an individual article wherein a selectedportion of the article may be encased in a carburizing compound, anotherportion of the article being free from the compound but subject to thegases therefrom whereby the latter portion may be increased in hardnessto.a degree differing from that of the encased portion.

Still a further object of my invention is the provision of a novelcarburizing container wherein selected portions of an article may beencased in carburizing compound, the container being formed of amaterial less resistant to carbunzing than the remaining portion of saidarticle whereby gases escaping from said carburizing compound to theother sections of the container will act upon the container wallsratherthan upon the adjacent portions of the article.

A further object is the provision of a novel carburizing apparatuswhereby selected portions of an article may be carburized without effecton other portions of the article in the absence of plating or otherprotective means.

Still a further object of my invention is to provide a novel carburizingapparatus whereby varying degrees of hardness may simultaneously beimparted to a single article by contacting a selected portion orportions of the article with carburizlng compound and subjecting otherportions of the article to the gases emanating from the compound.

The above and further objects will be more apparent from a study of thefollowing description when taken in connection with the accompanyingdrawings wherein:

Figure 1 is a top plan of a battery of carburiz ing containers embodyinga preferred embodiment of my invention,

Figure 2 is a side elevation taken partially in section substantiallyalong the line 2-2 of Figure 1,

Figure 3 is a side elevation partially in section similar to Figure 2,but illustrating a further preferred embodiment of my invention,

Figure 4 is an elevation of a section along a diameter of a furtherpreferred embodiment of my invention, and

Figure 5 is a partial plan view of Figure 4 with the cover andcarburizing compound removed.

A preferred embodiment of my invention will be described in connectionwith the carburizing of automobile rear axle drive pinion gears, but itwill be understood that I do not wish to be limited to this use. Othershapes and configurations are contemplated for differently formedarticles of manufacture and are intended to come within the scope of theappended claims.

Referring now to the drawings wherein like reference characters refer tolike parts wherever they occur, and with particular reference to Figure1, the apparatus inthis embodiment comprises two features-a base plate Iand carburizing containers 3. Base plate I is preferably an open grillsection and may be cast or built up from strip stock and welded orotherwise secured. Care must be taken that the members forming the grillare of substantially uniform section in order that uniform heating andcooling will occur.

The grill work, as shown, has longitudinal and .which form the remainingapertures 9 extend downwardly a lesser distance. Each of the feet II hasvertical slots I3 arranged in lateral alignment, which extend upwardlyof said feet and terminate in half-round slots, and the lower portionsof the alternate depending portion have half-round slots I I in similarlateral alignment,

said slots I4 preferably terminating in vertical alignment with slotsI3. These slots are for a purpose which will be evident hereinafter.

It is to be noted from the description of base I that it is of rigidconstruction and yet weighs very little. It is also to be noted thatbecause of the substantially uniform section thereof that there will belittle tendency toward warping.

Extending into the apertures 9 are lower cylindrical portions I5 ofcontainers 3. Referring to one container as an example, the outsidediameter of cylindrical portion I 5 is slightly less than the width ofthe apertures 9. This insures that even under high temperatures therewill be no binding of the containers in base member I. Above the portionI5 is a cylindrical portion I9 of larger diameter than portion I5, theupper end thereof being open and the lower end being joined to portionI5 by a circular wall or flange 2| which is adapted to rest upon theupper surface of base plate 8.

The lower portion of the container is loosely afixed to base plate I'bymeans of short rods or pins 23, which are inserted into slots I3 of feetII and slots I4, above described, and welded, or otherwise secured tothe closed end portion of cylindrical portion I5, as indicated at 25.Pins 23 are of slightly greater length than the outside width of feet II, thereby insuring that the lower portion of container 3 cannot partcompany with the base. It is also to be noted that a slight amount ofclearance is allowed between pin 23 and the upper portion of slots I3 toprovide for a full-floating relation.

The upper portion of container 3 comprises a cover having a longupstanding cylindrical portion 27 closed at its upper end and joined atits lower end to a larger cylindrical portion 29 by means of ahorizontal circular wall or flange 3i. The inside diameter of the largecylindrical portion 29 is slightly larger than the outside diameterofthe large cylindrical portion I9 of the lower portion of said container.Thus, as seen in Figure 2, cylindrical portion 29 overlaps cylindricalportion I9.

This overlapping is extremely important since it forms a seal whichprevents the articles within the containers from being subjected to anoxidizing atmosphere at carburizing temperatures. Such an atmospherewould cause the formation of scale on the articles and would turn thecompound to ash. The formation of scale would" destroy the close limitmachining previously given the articles and the formation of ash woulddestroy the effectiveness of the compound. During carburization, gas isgenerated by the compound and the overlapping relationship, above noted.prevents the generated gas from being displaced by the oxidizing gasesin the furnace.

A number of these containers'may be mounted on a single base. Asillustrated in the drawings,

there are fifteen containers on the onebase.

As above noted, the containers just described are particularly adaptedfor heat treating automotive rear axle bevel pinion gears. Such gearsare of the type generally shown in Figure 2 having an enlarged gearportion 33, a long shank or end portion 35 and in some cases a smallbearing piloting section 31 adjacent the gear portion.

and on the opposite side thereof from the shank 35. In such articles ofmanufacture it is necessary that the teeth of the gear be extremely hardand that the shank of the gear be comparatively soft. In practice, aRockwell C scale hardness of 58-65 is required on the gear teeth, and ahardness of 33-43 is required upon the shankportion. The reason for thisis that after carburizing a finishing die must be run over any threadsonthe shank and .in some instances splines or keyways cut in the endthereof. If this portion is harder than the above-noted 33-43, thenextreme dimculty isencountered in performing these operations.

Referring now to Figure 2, it will be noted that the piloting portion 31is dropped into the cylindrical portion l so that the shoulder betweensaid piloting portion 31 and the gear portion 33 cooperates with theupper side of the circular flange 2| to form a seal therewith.carburizing compound 39 is then packed around the gear portion 33 up tothe top of the lower portion IQ of the container. The cover of thecontainer is then put in place. This procedure is repeated for all ofthe containers of the battery. The battery is then placed into aheat-treating furnace where it is left fora period of hours until therequired depth of carbon penetration is obtained.

Upon removal from the furnace each cover is individually removed and thegear in said container is removed and quenched in oil before the nextcontainer cover is removed and the next piece removed and quenched. Thisinsures that the handling of each piece is individual and that thehandlers will be careful and avoid any nicking or scratching. of thearticles. This is important since metal at a temperature of about 1700F. may easily be scufied. Since the teeth of the gear portion 33 of thepinion gears are finish ground before carburiz ng, if any scufllng ornicking does take place during heat treat, it is necessary that the gearbe returned to the gear grinder for further finishing.

It is to be noted that after carburization and when the gears areremoved from their individual containers, only a very small portion ofthe compound will be removed after they are exposed to the air. When thecompound is at the carburizing temperature and is exposed to the air, itturns to ash. However, if it is not exposed to the air and is allowed tocool back to room or normal temperatures, then it may be used overagain. By reason of the small amount of lost compound, the cost ofcarburizing articles in this type of containers is accordingly" reduced.v 5 A further point to be noted is the very small amount of compoundneeded per pinion gear. The economy effected thereby is striking when itis considered that in the old single box construction, the weight ofcompound per pinion gear was 1% lbs. whereas in my invention only .lb.isrequired per gear. This results in a savings of approximately '15percent without consideration of the fact that a major amount of thecompound inaybe re-used.

. l6 This small amount of compound is conducive to a faster carburizingcycle for the filled containers are brought up to temperature faster.

quired heretofore 'for a given treatment of a certain article, thepresent invention has enabled a reduction to ten hours. Also, with thisdesign of apparatus the percentage rejection is reduced to percentandl'ess as compared to 4 percent for the single box type. Inconsidering the factors hitherto noted and other items of cost, it hasbeen determined that by employing the present invention, the cost ofheat treating the gears is reduced 21 percent over the prior single boxtype.

It is to be noted that the shank portion of the gears, while not incontact with the-carburizing compound, during the heating operation, isexposed to the gases emitted by the compound. While the efiect of thegases is not very 35 great due to the formation of a gas pocket in thecylindrical portion 21 of the containers, and a correspondingrestriction of circulation of the carburizing gases, the small amount ofgas that does circulate, plus the oil quench which is given the partsafter being heated, imparts to the shank portion just the degree ofhardness requred for the transmission of torque. This hardness, as abovenoted, for the particular gears described, is the Rockwell C scalehardness of 33-43.

In the event a greater hardness differential is required the covers orupper portions of the containers 3 may be of a simple low carbon steelrather than the special carburizing resistant 50,

steel which is at present used. In this case any gases which maycirculate within cylindrical portion 21 will act upon the containerrather than the article therein. While the life of such covers would notbe as long as those made from special container material, as excessivecarburization would make them extremely brittle, their cost ismaterially less, so that even thoughmore covers are necessary, the costper article carburized is not increased. '6

It is also to be noted that the portion 31 of said gears which extendsinto the lower cylindrical portion i5 of said containers issubstantially sealed from the carburizing gases by reason of theengagement of the shoulder intermediate the gear tooth portion 33 andthe bearing pilot portion 31 with the upper portion of circular flange21. Any gases that may leak into said chamber will only have an efiectsimilar to that described for the cylindrical portion 21.

Referring now to the preferred embodiment illustrated in Figure 3, thecontainers bear some resemblance to those illustrated in the abovenotedMcQuaid application, having a long cylindrical body portion 4| with aclosed bottom 43. 75

"Reversible covers 55 are provided for the open tops of the cylindricalportions and have-overlapping cylindrical portions thereon. Thisoverlapping arrangement has the same function as previously described inconnection with the overlapping arrangement of Figure 2.

Centrally attached to the lower portion or base '43 of said container isa cylindrical portion 43 which is adapted to project into apertures 91:of the base la much in the same manner as the cylindrical portion l ofthe containers ll of Figure 2 projects into the apertures 3. In likemanner, rods or pins 23a are welded to the lower portion of cylindricalportions 49, thus retaining the containers loosely within the base id.

As a stabilizing measure, in the event that the containers are inclinedto be top-heavy, an upper structure is provided for the base la, whichcomprises a lateral and longitudinal grill work 50 which may be castintegral with base Ia, or may be of a built-up welded section andcomposed of strips of steel. The upper structure forms apertures 5|, thewidth of which is greater than the outside diameter of the cylindricalportion M of said containers which are thereby loosely confined inupright position.

The containers illustrated in Figure 3 are extremely satisfactory and aseconomical as those of Figure 2 for substantially cylindrical parts ofnearly the same size as: the containers, or for small parts which may bestacked one on top of the other (as shown) and thus form substantially acylinder.

Referring now to Figures 4 and 5, there are some automotive parts whichrequire that only a portion have a hard surface, but which it would behighly impractical to give individual handling. Such parts are steeringarm balls, as used in conjunction with steering axles. These partsrequire that only the head or spherically rounded portion shall be hard.As it is inherent in the design of these parts that a comparatively deepundercut portion be adjacent the spherical or head portion, it is highlyimportant that no carburization take place in this undercut portion.Failure to take this precaution usually results in breakage of the partat the undercut. The present practice of carburizing these parts is tofinish the parts all over and copper-plate all but the portion of thehead or spherical portion which is to be hardened. The entire part isplaced in a carburizing pot and carburized. and after carburization thecopper-plate is removed. Then the shank of the ball must be properlytempered.

I have illustrated in Figures 4 and 5 a further preferred embodiment ofmy invention in the way of an improved apparatus for carburizing suchparts as steering balls whereby carburization will only take place atthat portion where it is required and wherein operations ofcopperplating and removing copper plate and tempering are eliminated.

This apparatus comprises a preferably circular box structure 52 havingan open top. Inserted therein is an apertured plate 53 which issuspended part way downand on the inside of the box by means of support55. Support 55 comprises in effect a cylindrical member terminating atits lower portion in an inwardly turned lip upon which plate 53 restsand at its upper portion in an outwardly turned lip whereby the support55 and plate 53 are supported upon the upper edge of box 52. Suspendedfrom plate 53 by means of long bolts 51 is a second plate 58 which isapertured in alignment with the apertures in plate 53.

The steering balls 5| are inserted vertically through the apertures inplates 53 and 59. The apertures in plate 53 are of such size that theportion of the heads of said balls which are to be hardened areprevented from passing therethrough. The apertures in plate 53 are forthe purpose of preventing said steering balls from being displaced toofar out of vertical alignment. If desired, nuts may be threaded onto thethreaded ends of said balls and secured against the lower side of plate59 to insure such alignment as shown at 60.

Carburizing compound is packed around the spherical and portions whichproject above plate 53 and is leveled off with the top of support 55. Acover 53 is then placed upon the top of the box, the cover having adepending lip portion 55 which overhangs on the outside of box 52.Suitable eyes 51 and 69 may be provided in cover 65 and plate 53respectively for convenient handling. A small amount of carburizingcompound may be sprinkled in the bottom of box 5| to insure that anoxidizing atmosphere will not be present in the vicinity of the shankends of balls 5| during caburizing.

It is thus seen that only a predetermined portion of the spherical endsof the steering balls will be carburized, as the lower portion of thebox is effectively sealed from the bulk of the carburizing gases. Suchgases as may leak into the lower chamber will have the effect beforedescribed in connection with the shank 35 of the gear of Figure 2. Sinceit has heretofore been necessary to temper the end portions of theballs, the above described effect is very desirable in giving the endportions an intermediate hardness and thus eliminating the temperingoperation.

From the above and foregoing description, it is evident that myinvention comprises carburizing apparatus which effectively overcome thedisadvantages of prior practices and have distinct advantages thereover,including the following:

1. Carburization of only those portions which require carburizing.

- 2. Automatic heat treatment of portions not carburized.

3. Use of extremely small amounts of carburizing compound and small lossthereof.

4. Absence of oxidizing atmosphere within the containers.

5. comparatively small time in the furnace.

6. Guarantee of individual handling.

7. Low percentage of rejection.

8. Parts are in upright position, thereby substantially eliminatingwarpage.

9. Elimination of costly operations subsequent to carburization.

10. Reduction in cost per article carburized.

11. Full floating containers in battery arrangement.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictuve, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meanning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. A heat-treatment container for supporting a manufactured articlehaving an enlarged portion, said container being formed to substantiallyconform to the shape of said article and enlarged adjacent said enlargedportion of said article to provide for the use of a heat treatingcompound and formed with a section to directly engage and co-operatewith said enlarged portion of said article to substantially protectother portions of said article from the action of said heat treatingcompound.

2. In a heat treating apparatus for manufactured articles, a pluralityof individual containers arranged to support said articles, a basemember associated with said containers and means to secure saidcontainers directly to said base member in full floating relationtherewith.

3. In a heat treating apparatus for manufactured articles, a base membercomprising a series of members arranged in angular relation to oneanother to form a series of pockets, containers arranged to fit withinsaid pockets, and means to looselysecure said containers within saidpockets.

4. In a heat treating apparatus for manufactured articles, a base membercomprising a series of members arranged in angular relation to oneanother to form a series of pockets with slots in the lower portionsthereof, containers arranged to fit within said pockets, and means toengage said slots and said containers to loosely secure said containerswithin said pockets.

5. In an apparatus for heat treating a manufactured article having anenlarged portion and projecting end portions, a container comprising asection generally conforming to said article, a shoulder between theends of said section arranged to be engaged by said enlarged portion ofsaid article to define a zone for the reception of heat treatingcompound and a zone for receiving one of said projecting end portionssubstantially sealed from said compound, and an additional sectionarranged to engage an end .of said first section in sealing relation andof a shape to conform to the other said projecting end portion of saidarticle.

6. In an apparatus for heat treating a manufactured article having anenlarged portion and a projecting end portion, a container comprising asection generally conforming to said article, said section beingenlarged adjacent said enlarged portion of said article for thereception of a heat treating compound, and an additional sectionarranged to engage said first section in sealing relation thereto and ofa shape to conform to the projecting portion of said article, saidsecond section being arranged to receive gases from a heat treatingcompound in said first section.

7. In a heat treating apparatus for manufactured articles, a base membercomprising a series of members arranged in angular relation to oneanother to form a series of pockets, containers with ends thereofarranged to fit within said pockets, means to loosely secure said endsof said containers within said pockets, and meanssecuredtosaidbaseandarrangedtosupport the opposite ends of saidcontainers.

iii A container for heat treating manufac tured articles comprising arelatively deep section open at the top thereof, and a tray engaging thesides of said section to support articles to be heat treated and toconfine the heat treating compounds adjacent selected portions of saidarticles, said tray being formed to cooperate with portions ofsaidarticles to substantially seal the remaining portion of saidarticles from said heat treating compound.

9. A container for heat treating manufactured articles comprising arelatively deep open ended box section, a tray mounted adjacent theupper end of said section and arranged to seal the edges thereof, saidtray being formed with apertures in the bottom thereof of a size toreceive articles to be heat treated and maintain said articles insuspended relation, and heat treating compound in said tray, and meansto seal said section and said tray to prevent the access of an oxidizinggas thereto.

10. A container for enclosing and supporting an article for selectiveheat treatment, said container comprising means providing adjacentchambers, a wall member intermediate of said chambers having an articlesupporting surface thereon, said surface being adapted to engage aportion of an article to be treated and to individually support saidarticle with portions thereof in each of said chambers, said surface andsaid portion cooperating to isolate said chambers, and a cover for saidcontainer.

11. A heat-treating container for enclosing and individually supportingan article to be selectively treated and characterized by having an :2enlarged portion to be treated by carburizing compound and anotherportion to be isolated from said compound during treatment; saidcontainer comprising, means forming a first chamber for holdingcarburizing compound and for receiving the enlarged portion of anarticle to be treated and a second chamber for receiving another portionof the article, a supporting means associated with said first namedmeans for supporting the article, said last named means being arrangedto directly contact the enlarged portion of the article to isolate theother portion thereof from carburizing compound in said first mentionedchamber, and a cover for said container for sealing said chambers fromfurnace gases.

12. A heat-treating device comprising a container, said container beingformed to provide adjacent chambers, one of said chambers being arrangedabove the other and adapted to receive carburizing compound and toenclose an enlarged portion of an article to be treated, the other ofsaid chambers being adapted to enclose another portion of the article,means on said container adjacent said chambers for directly engaging theenlarged portion of the article to individually support the article insaid container, said last named means being arranged to cooperate withthe enlarged portion of the article to seal said second chamber fromsaid first chamber whereby the other portion of the article will beisolated from carburizing compound in said first chamber duringtreatment, and means for closing said container.

ammr c. m.

